Removal of wax from hydrocarbon oil



Nv. 3o, 1937.

ATTORNEY Patented Nov. 30, 19137 UNirED STATES 2,100,915 REMOVAL F WAX BOM HYDROCARBON .IL

Ernest F. Pevere, Beacon, N. Y., assigner to The Texas Company, New York, N. Y., a corporation of Delaware Application May z5, 1934, serial No. '121,385

11 Claims.

This invention relates tothe dewaxing of wax bearing oil, and particularly to the separation of wax from a, mineral lubricating oil.

The invention contemplates the separation .of

.wax from such a waxy bearing oil by the employment of an organic ester as a wax crystal modifying material, to facilitate dewaxing by centrlfuging, cold settling or filtration. In accordance with the present invention, the wax crystal modifying material is added to a wax bearing oil, and the oil then chilled with resultant precipitation of wax in a fornrwhich is found to.

facilitate separation by centrifuging'or cold settling, and which is also found to materially in- 5 crease ltering rates where the wax is separated by ltration. f

Various types of organic esters are suitable forA purposes of the present invention. For example,

glycerol esters of fatty acids, and particularly.

the higher saturated fatty acids, such as glycerol tristearate, glycerol tripalmitate, etc., constitute highly effective wax crystal modifying materials. The glycerol mono.- and diesters of these fatty acids may also be employed, where the solubility 25 characteristics of the esters in the particular oil being treated permits the solution of a suiiicient quantity, such for example as 0.5% to about 5.0% or more by weight.

The various glycol esters of fatty acids, and 30 particularly the higher saturated fatty acids, are also very satisfactory for purposes of the present invention. For example, ethylene glycol dlstearate, ethylene glycol dipalmitate, and the corresponding mono-esters of ethylene glycol, are very satisfactory.

.Fatty acid esters of polyhydric alcohols higher than glycerol, such as the tetrahydric alcohol erythritol, and the hexahydric alcohols, such as mannitol and sorbitol, are also satisfactory. For example, mannitan tetrastearate is found to be highly eective. K

Fatty acid estersof higher molecular weight monohydric alcohols having 6 or more carbon atoms to the molecule, such for example as hexyl, heptyl, octyl and cetyl alcohols, may likewise be employed. Cetyl stearate is an example of an' effective ester of this class.

In addition to the fatty acid esters mentioned above, the esters formed from the above-mentioned alcohols with acids derived from oxidized paraffin wax, or other waxy hydrocarbons, may also be employed.

An ester, or mixture of esters, from the classes mentioned above, maybe employed in minor proportions with a wax bearing oil to be treated. In general, lit may be stated that a proportion of from about 0.5% to 10% by weight may be used. However, the beneficial effect of lthe ester addi tion generally increases with anincrease in proso portion up to a certain denite amount; and

further addition then may produce no additional beneficial effect, and in fact may decrease the effectiveness. The mostadvantageous proportion can be readily determined by tests with the particular ester and the particular wax bearing oil employed.

The organic ester of the character described above is preferably employed in conjunction with .a dewaxing solvent or solvent mixture. Various solvents can be used for this purpose, such for example as acetone, ethylenedlchloride, methyl ethyl ketone, naphtha, various aliphatic alcohols and the like. Very satisfactory results are secured by the use of a mixture of `a wax solvent with a non-solvent, such as a mixture of benzol and acetone, for instance in lthe proportions of 65% benzol to 35% acetone. Another very satisfactory solvent mixture of this character, particularly for use in the dewaxing of residual oils, consists of 28-35% acetone, 4757%benzol and -18% toluol. .A comminuted filter aid .niaterial of the character of infusori'al or diatomaceous earth may also be employed in conjunction with the wax crystal modifying material, and also with the solventor solvent mixture. The filter aid material may be added prior to, during or after chilling.

By way of example, the invention is hereinafter particularly described and illustrated in the accompanying drawing, in which the single gure is a flow sheet of the method, wherein glycerol tristearate is prepared and utilized as a dewaxing aid. As shown, glycerine and commercial stearic acid from supply tanks Ill and Il respectively, are supplied toan esterication vessel I2, where the ester is formed in conventional mannerysuch as that suggested by Bellucci (Journal of the Chemical Society, Abstracts, 1911, Volume I, page 416). Ether is added from tank I3 to form a solution of the reaction product, and the, solution passed to washing tank i4, where it is washed with weak caustic solution and then with distilled water from suitable Sources of supu ply l5 and I6, to remove free fatty acids.` rl'he washed solution is then distilled in still I1 to remove the ether which is condensed in condenser iB and returnedto storage i3 for reuse. The puried glycerol ester is passed to storage I8.

The wax crystal modifying material is in a suitable mixer 'and agitator 20. The proaddetl from tank i8 to a wax bearing oil from storage i9 portions in which the modifying material can be erol ester material prepared as outlined above, generally provides satisfactory results. The glycerol ester may be added directly to the lubricating oil in which it is readily soluble; or a solution of the ester may be first prepared in a suitable solvent, such as a lubricating oil or a dewaxing solvent, and the solution added to the wax bearing oil to give the desired proportion of ester in the mixture.

A dewaxing solvent from storage tank 22 is preferably added to the Wax bearing oil. By way of example, a solvent mixture of 35% acetone and 65% benzol in the proportions of 1 part of oil to 3 parts of acetone-benzol mixture is herein described. The oil mixture is then passed through chilling coils 23 where it is chilled to a temperature of around 0.to 10 F. A lter aid material from the hopper feed 24 may be supplied by line 25 to the agitator 20, so that the oil is chilled in the presence of the filter aid material. Or, the filter aid material can be supplied by line 26 to the already chilled oil as the latter is fed to a filter 21. Or, al proportion of filter aid can be added both before and after chilling. The filter 21 may be of any suitable conventional construction, such for example, as a pressure filter or a continuous filter. The solids including wax are removed by the filter and passed to a receiving vat 28, while the filtrate of dewaxed oil andv solvent passes to a solvent recovery still 29. Here, the solvent is distilled from the dewaxed oil, and passed to a receiving tank 30, from which it may be returned to the storage tank 22 for reuse in the process. The dewaxed oil is accumulated in a receiving tank 3l.

Where a solvent mixture of the character of acetone-benzol or acetone-benzol-toluol is employed, the resulting wax free oil is found -to have a pour test of around 0 F. when chilled only to about 0 F. or slightly below. The ltering rates of the chilled oil may be improved as much as 100% to 150% above those obtained when a similar chilled mixture omitting the wax crystal modifying material, is employed. Where the wax bearing oilmixtures containing the wax crystal modifying material is chilled to about 10 F. and subjected to cold settling, it is found that more rapid settling of the solid constituents occurs, and a clear supernatant liquid layer of oil and solvent may be readily drawn o from the settled solids. When the solvent is then removed.

by distillation, a substantially wax free oil of low pour test of around 0 F. is obtained. Where the chilled mixture containing the wax crystal modifying material is subjected to centrifuging, im-

proved separation ofthe wax from the oil results.

giving a wax-free oil of the desired low pour test.

As a further example, ethylene glycol distearate may be prepared from commercial stearic acid by reacting ethylene chloride with the potassium salt of stearic acid according to the following equation: calci' onltormlooocrr,

vThe resulting product may then be purified by the ether to obtain the ester as a white' solid. The ester is then added to a wax bearing oil, preferably in the proportion of about 1% to 5% by weight, together with a dewaxing solvent or solvent mixture of the character described above. The oil mixture is then chilled to cause precipitation of the wax, and the Wax then separated in the manner previously described.

`When in the claims I use the words fatty acid, I refer to the aliphatic acids generally obtained from commercial fats and oils. It is understood that I do not refer to acetic acid and its immediate homologs.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. The method of dewaxing a wax bearing oil, which comprises mixing with the oil an organic ester which has the property of modifying wax crystal formation upon chilling of the oil in the presence thereof, the said ester being selected from the group consisting of fatty acid esters of glycerol, fatty acid esters of glycols, fatty acid esters of monohydric alcohols selected from the group consisting of hexyl, heptyl, octyl and cetyl alcohols, fatty acid esters of polyhydric alcohols of the series higher than glycerol selected from the group consisting of erythritol, mannitol and sorbitol, and esters of the above-mentioned alcohols with the acids. derived from oxidized waxy hydrocarbons, chilling the mixture to precipitate the Wax, and separating the wax from the oil.

2. The method of claim 1, in which the ester isa glycerol ester of a saturated fatty acid.

3. 'I'he method of claim 1, in which the ester is glycerol tristearate.

4. The method of claim 1, in which the ester is a glycol ester of a saturated fatty acid.

5. The method of claim 1, in which the ester .is ethylene glycol distearate.

6. The method of claim 1, in which the ester is a hexahydric alcohol ester of a saturated fatty acid.

7. The method of claim 1, in which the ester is mannitan tctrastearate.

8. The method of claim 1, in which the wax is separated from the oil by ltration, and in which the ester servesto materially increase the filtration rate.

9. 'I he method of claim 1, in which a dewaxing solvent is also added to the wax bearing oil prior to wax separation, the solvent being of such character that the normally liquid and normally solid constituents of the oil are soluble therein at elevated temperatures of the order of 100 F. and above, and the normally liq-uid constituents are soluble while the normally solid constituents are substantially completely insoluble therein at lowered temperatures ofthe order of 0 F. and below.

10. 'I'he method of claim 1, in which a dewaxing solvent comprising acetone and benzol is added to the wax bearing oil prior to wax separaion.

11. The method vof claim 1, in which a filter aid material is added to the wax bearing oil prior to wax separation.

ERNEST F. PEvEaE. 

